Polymer electrolyte fuel cell, electrode for it and method for producing it

ABSTRACT

An electrode for a polymer electrolyte fuel cell, which is a porous gas diffusion electrode comprising a catalyst powder and an ion exchange resin, wherein a solvent-soluble fluorine-containing polymer having substantially no ion exchange groups exists at least at a part of the inner surface of pores of the electrode.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a polymer electrolyte fuel cell,an electrode for it and a method for producing it.

[0003] 2. Discussion of Background

[0004] Attention has been drawn to a hydrogen-oxygen fuel cell as apower generation system which gives no adverse effect to the globalenvironment, since the reaction product is only water in principle. Avery high output is expected at a low operation temperature of from roomtemperature to about 150° C., which is being studied recently. In such acase, it is assumed to use, as a fuel, hydrogen gas obtained byreforming a hydrocarbon such as methane, methanol or gasoline andcontaining e.g. carbon dioxide.

[0005] On the other hand, polymer electrolyte fuel cells have a lowoperation temperature. Accordingly, exhaust heat can hardly be utilized,for example, as an auxiliary power, and it is utilized only for hotwater at best. To offset such a drawback, it is necessary for thepolymer electrolyte fuel cell to secure a high output density. Further,for practical application, it is required to secure performance of ahigh energy efficiency and a high output density even under an operationcondition where the fuel and air utilization ratios are high.

[0006] As the electrolyte for the polymer electrolyte fuel cell, aperfluorocarbon sulfonic acid type cation exchange membrane, which is anultrastrong acid, is mainly used, in view of the chemical stability andelectric conductivity. When such an acid electrolyte is used, thefollowing reaction occurs at an air electrode, whereby water will beformed.

[0007] 1/2O₂+2H⁺+2e⁻→H₂O

[0008] Therefore, under such an operation condition as a low operationtemperature, a high current density and a high gas utilization ratio,clogging (flooding) at the pores of the electrode body is likely to takeplace due to condensation of steam, at the air electrode where water isformed. Accordingly, in order to obtain a stable performance of the fuelcell for a long period of time, it is necessary to secure waterrepellency of the electrode so as to prevent such flooding. This isparticularly important in the case of a polymer electrolyte fuel cellwhereby a high output density at a low temperature is desired.

[0009] To impart water repellency to the electrode, it has been studiedto incorporate a fluorine-containing material to the electrode.Specifically, for example, the following methods (1) to (3) have beenproposed. (1) A method in which a catalyst carrier is subjected to afluorination treatment (JP-A-7-192738). (2) A method in which afluorine-containing polymer is incorporated in the electrode(JP-A-5-36418). (3) A method in which a fluorinated pitch isincorporated in the electrode (JP-A-7-211324).

[0010] Among these, a fluorination treatment such as the method (1)requires a special equipment or technique, and thus it is unsuitable asa means to directly reform the surface of the carrier of the catalyst.

[0011] A fluorine-containing polymer which is insoluble in a solvent isused for the method (2). Specific examples include atetrafluoroethylene-hexafluoropropylene copolymer (hereinafter referredto as FEP), a tetrafluoroethylene-perfluoro(alkyl vinyl ether) copolymer(hereinafter referred to as PFA) and a polytetrafluoroethylene(hereinafter referred to as PTFE). In the present specification, a A-Bcopolymer means a copolymer having polymer units based on A and polymerunits based on B.

[0012] To incorporate such a fluorine-containing polymer in theelectrode as a water repellent, it is used in the form of a powder or adispersion of the powder. The method of forming an electrode layercontaining the fluorine-containing polymer, may, for example, be amethod in which the dispersion of the fluorine-containing polymer ispermitted to penetrate into pores of the electrode after the electrodelayer is formed (2-1), or a method in which a powder or a dispersion ofthe fluorine-containing polymer is mixed with the rest of material whichforms the electrode and then the electrode layer is formed (2-2).

[0013] The pore size of the gas diffusion electrode for a fuel celldepends on the method of producing the electrode. However, in general,the pore size distributes from about 0.01 to about several hundreds μm.If the water repellency in pores is inadequate, clogging is likely tostart from pores having a small pore size due to capillary phenomenon,in general. Accordingly, it is considered that if water repellency isimparted to the inside of pores having a pore size of at least 0.05 μm,clogging of pores due to condensed water decreases, a quick electrodereaction can be made possible, and fuel cell properties will improve.

[0014] However, the primary particle size of the solvent-insolublefluorine-containing polymer is about 0.1 μm at smallest. Further, in thecase where it is supplied in the form of a powder, it is usuallygranulated, and thus the average particle size is from about several μmto about 500 μm. Accordingly, it was difficult to let thesolvent-insoluble fluorine-containing polymer penetrate to the inside ofpores having a pore size of about 0.05 μm, by means of impregnation,spray or filtration, after the electrode layer is formed. Namely, it wasdifficult to adopt the method (2-1), and the electrode layer was formedby the method (2-2).

[0015] On the other hand, in the method (2-2), a catalyst, a catalystcarrier and a conductive agent powder are mixed with thesolvent-insoluble fluorine-containing polymer to prepare an electrode.Generally, carbon black is used for the catalyst carrier or theconductive agent, and the particle size is from 0.02 to 0.05 μm. Namely,the particle size of the fluorine-containing polymer is larger than theparticle size of carbon black. Accordingly, if the electrode is preparedby this method, the solvent-insoluble fluorine-containing polymer as awater repellent exists ununiformly in the electrode layer in the form ofparticles. Therefore, with this method, the inside of pores could notnecessarily be made water repellent uniformly, although the pore sizecould be made large. Further, the solvent-insoluble fluorine-containingpolymer is non-electroconductive. Accordingly, if the amount of thewater repellent is increased in order to improve water repellency of theelectrode, the resistance of the electrode may increase.

[0016] In the method (3), a polymerization reaction may take place inthe process for producing the fluorinated pitch, and the fluorinatedpitch is a polymer in a broad sense. In a case where the fluorinatedpitch is insoluble in a solvent, there will be the same problems as inthe method (2). Some fluorinate pitches are soluble in a fluorine-typesolvent. In this case, the fluorinated pitch has a relatively lowmolecular weight at a level of from about 1,000 to about 3,000, and asix-membered plane structure, whereby the bonding force among moleculesis weak, the film-forming property after drying is inadequate, and thefluorinated pitch is likely to fall off, so that durability isinadequate. Further, bonding between a carbon atom and a fluorine atomin the fluorinated pitch is likely to be cut in the presence of analkali, and it is not sufficiently stable also in this respect.

SUMMARY OF THE INVENTION

[0017] It is an object of the present invention to provide an electrodefor a polymer electrolyte fuel cell which is capable of keeping anadequate water repellency for a long period of time, and to provide afuel cell having a stable performance for a long period of time, byusing the electrode.

[0018] The present invention provides an electrode for a polymerelectrolyte fuel cell, which is a porous gas diffusion electrodecomprising a catalyst powder and an ion exchange resin, wherein asolvent-soluble fluorine-containing polymer having substantially no ionexchange groups exists at least at a part of the inner surface of poresof the electrode, and a polymer electrolyte fuel cell having theelectrode.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The electrode for a polymer electrolyte fuel cell of the presentinvention contains a solvent-soluble fluorine-containing polymer havingsubstantially no ion exchange groups, which imparts water repellency tothe electrode. The fluorine-containing polymer is not particularlylimited so long as there is a solvent capable of dissolving it. However,preferred is a fluorine-containing polymer which is hardly soluble in asolvent such as an alcohol or water which may be a reactant or reactionproduct in the electrode reaction of the fuel cell.

[0020] Further, the fluorine-containing polymer may be partiallyfluorinated or totally fluorinated. However, it is preferably in a solidstate at a temperature within a range where the polymer electrolyte fuelcell is used, and specifically, it is preferably in a solid state at atemperature of from room temperature to 150° C. Further, thefluorine-containing polymer of the present invention has substantiallyno ion exchange group. Specifically, the amount of the ion exchangegroup such as a sulfonic acid group or a carbonic acid group, ispreferably at most 0.1 meq./g dry resin, particularly preferably at most0.05 meq./g dry resin.

[0021] As the fluorine-containing polymer, a perfluorocarbon polymerhaving an alicyclic structure in the molecule is preferred. Such apolymer is hardly crystallizable due to twisting of the moleculeattributable to the molecular structure, and it is soluble in afluorinated solvent. Examples of the polymer include ones having cyclicstructures of the following formulae, i.e. polymers having cyclicstructures of the formulae 1 to 3 as polymer units. Among these, afluorine-containing polymer having polymer units of any one of thefollowing formulae 4 to 12, is preferred.

[0022] wherein 1 is an integer of from 0 to 5, m is an integer of from 0to 4, n is an integer of from 0 to 1, 1+m+n is from 1 to 6, and R is For CF₃;

[0023] wherein each of o, p and q which are independent of one another,is an integer of from 0 to 5, and o+p+q is from 1 to 6;

[0024] wherein each of R₁ and R₂ which are independent of each other, isF or CF₃.

[0025] Such a fluorine-containing polymer can be dissolved in afluorinated solvent such as perfluorobenzene, trifluoroethane, AFLUDE(tradename of a fluorinated solvent manufactured by Asahi Glass CompanyLtd.), or perfluoro(2-butyltetrahydrofuran), or in a solvent containingpolyfluoroalkyl groups, and a solution having a concentration of from0.01 to 50 wt % can be obtained.

[0026] As the fluorine-containing polymer of the present invention, apolymer made by partial fluorination of a non-acrylic resin may bepreferably used, in addition to polymers of the formulae 1 to 3.Specifically, preferred is a copolymer having polymer units based on afluoroolefin and polymer units based on at least one monomer selectedfrom the group consisting of a vinyl ether, a vinyl ester, an allylether, an allyl ester, an isopropenyl ether, an isopropenyl ester, anacrylic ester and a methacrylic ester.

[0027] As the vinyl ether, an alkyl vinyl ether such as ethyl vinylether, butyl vinyl ether or cyclohexyl vinyl ether, a (fluoroalkylvinyl)ether or a (perfluoroalkyl vinyl)ether made by partial or totalfluorination of hydrogen atoms of the alkyl vinyl ether may, forexample, be mentioned. As the vinyl ester, a fatty acid vinyl ester suchas Beobar-10 (tradename of a commercial product manufactured by ShellChemical) having branched alkyl groups, vinyl acetate, vinyl butyrate,vinyl pivalate or vinyl batatiate may, for example, be mentioned. Thehydrogen atoms of the vinyl ester may be partially or totallysubstituted with fluorine.

[0028] As the allyl ether, an alkyl allyl ether such as ethyl allylether or cyclohexyl allyl ether may, for example, be mentioned. As theallyl ester, a fatty acid allyl ester such as allyl propionate or allylacetate may, for example, be mentioned. As the isopropenyl ether, analkylisopropenyl ether such as methylisopropenyl ether may, for example,be mentioned. The hydrogen atoms of the allyl ether may be partially ortotally substituted with fluorine.

[0029] With regard to the copolymer having polymer units based on afluoroolefin, the polymer units based on a fluoroolefin are containedpreferably in an amount of from 30 to 70 mol %, particularly preferablyfrom 40 to 60 mol %, since if the ratio of the polymer units based on afluoroolefin is excessively large, the solubility in a solventdecreases.

[0030] The polymer obtained by partial fluorination of the non-acrylicpolymer can be dissolved in at least one member selected from the groupconsisting of a ketone, an ester, a chloroethane and a benzenederivative, and the concentration of the solution can be made from 30 to70 wt %.

[0031] The perfluorocarbon polymer having an alicyclic structure in themolecule and the polymer made by partial fluorination of a non-acrylicresin, which are mentioned above as the solvent-solublefluorine-containing polymers, are hardly decomposable to a monomer, andthus they are not likely to undergo radical propagation, and excellentin acid resistance and alkali resistance.

[0032] The molecular weight of the fluorine-containing polymer of thepresent invention is preferably from about 2,000 to about 200,000,particularly preferably from about 5,000 to about 10,000. In the casewhere the weight concentration of the solution of thefluorine-containing polymer is same, in general, the larger themolecular weight of the polymer, the higher the viscosity of thesolution having the polymer dissolved in the solvent. When using apolymer having a molecular weight within the rage as defined above, inthe case where the electrode is impregnated in the solution of thefluorine-containing polymer to impart water repellency to the electrode,it is possible to keep the viscosity of the solution at a level wherepenetrability of the solution to the electrode is adequate, and at thesame to obtain adequate adhesion to the surface of pores of thefluorine-containing polymer, and to maintain the water repellency of theelectrode for a long period of time.

[0033] The electrode for a polymer electrolyte fuel cell comprises acatalyst powder, an ion exchange resin and a fluorine-containing polymerhaving substantially no ion exchange group and being soluble in asolvent. In addition, carbon to increase conductivity, a binder or abase material such as a fiber to maintain the shape, or a moisturizersuch as SiO₂ or TiO₂ to absorb water, may be incorporated.

[0034] Various methods can be employed for producing the electrode for apolymer electrolyte fuel cell, by using the solution of thefluorine-containing polymer of the present invention. For example, it ispossible to mix a solution having the fluorine-containing polymerdissolved, with a catalyst powder or an ion exchange resin which isanother component to form the electrode, to form the electrode. It isalso possible to spray or impregnate the solution to the electrode afterthe electrode is formed from such another component. Further, in a casewhere water repellency of the electrode has decreased after the fuelcell is used, it is possible to impart water repellency again to theelectrode, by using the solution, i.e. by impregnation or spraying, asthe case requires.

[0035] In the present invention, the solution having thefluorine-containing polymer dissolved can be used. Therefore, even ifthe particle size of another electrode-constituting material is small,or no matter how small the pore size of pores of the electrode, thefluorine-containing polymer exists on the inner surface of pores of theelectrode after the solvent was removed by drying. The amount of thefluorine-containing polymer of the present invention existing in theelectrode is preferably from 0.001 to 30 wt %, more preferably from 0.01to 20 wt %.

[0036] As a method of producing the electrode for a polymer electrolytefuel cell of the present invention, a known method such as spraying,coating or filtration of a mixed liquid comprising a catalyst powder ofplatinum-black or platinum supported on activated carbon, an ionexchange resin and, and if necessary, a pore forming agent, a thickeneror a diluting solvent, is preferably employed. The water repellent maybe preliminarily mixed in the mixed liquid, as mentioned above.

[0037] When producing a polymer electrolyte fuel cell using theelectrode of the present invention, as a method of bonding the electrodeand the ion exchange membrane as a solid polymer electrolyte, a methodof directly forming the electrode on the ion exchange membrane, a methodof forming the electrode in the shape of a layer on the substrate suchas carbon paper, then bonding the electrode with the ion exchangemembrane, or a method of forming the electrode on a plate andtransferring the electrode to the ion exchange membrane, is preferablyemployed. When the electrode is formed separately from the ion exchangemembrane, as the method of bonding the electrode to the ion exchangemembrane, a hot press method or a bonding method (JP-A-7-220741,JP-A-7-254420) may, for example, be employed.

[0038] The ion exchange resin and the ion exchange membrane as a solidpolymer electrolyte, contained in the electrode of the presentinvention, are preferably made of a fluorocarbon sulfonic acid type ionexchange resin or a fluorocarbon phosphonic acid type ion exchangeresin. Particularly preferably, they are made of a perfluorocarbonsulfonic acid type ion exchange resin comprising a copolymer havingpolymer units based on CF₂=CF₂ and polymer units based onCF₂=CF−(OCF₂CFX)_(m)−O_(p)−(CF₂)_(n)−SO₃H, wherein m is an integer offrom 0 to 3, n is an integer of from 1 to 12, p is 0 or 1, and X is F orCF₃, is preferred.

[0039] It is preferred to use PTFE, FEP, PFA or the like as the binderfor the electrode of the present invention, and the amount is preferablyfrom 0.01 to 30 wt % to the electrode. Such a binder has a function alsoas a water repellent. Further, it is preferred that the electrodecontains a thickener of ethyl cellulose type, methyl cellulose type orcellosolve type.

[0040] Further, when forming the electrode, a diluting solvent may beused. As the diluting solvent, a fluoroalkane, a fluorotrialkylamine, afluoroalkyltetrahydrofuran, a ketone, an ester, a chloroethane, abenzene derivative, an alcohol such as methanol, ethanol or isopropanol,a fluorocarbon, a hydrofluorocarbon, a hydrochlorofluorocarbon or watermay, for example, be used.

[0041] The electrode of the present invention has a water repellencyequal to or more than the ordinary electrode, and at the same time, theamount of a non-electroconductive resin can be made small, whereby theelectrode can be made thin. Accordingly, it has an excellent gasdiffusion property and low resistance, whereby it can be effectivelyused as both an air electrode and a hydrogen electrode. Further, it ispossible to use the electrode of the present invention as an electrodeat which water is formed by the reaction, and to use an electrode havingno water repellency as the other electrode, to obtain a fuel cell havinghigh reliability for a long period of time.

[0042] In the present invention, a solution of the solvent-solublefluorine-containing polymer is used. Therefore, it is possible touniformly coat the surface of the catalyst in the pores of the electrodeby the fluorine-containing polymer, and to impart an adequate waterrepellency to the electrode by the fluorine-containing polymer, even ifthe amount of the fluorine-containing polymer is small. Further, in thecase where the fluorine-containing polymer is incorporated to theelectrode by e.g. impregnation or spraying, after the electrode isformed, it is easy to secure durability for the water repellent coatingfilm obtained by drying, since the solution of the fluorine-containingpolymer of the present invention has a film-forming property.

[0043] Further, in the production process to impart water repellency tothe electrode, it is possible to impart water repellency to theelectrode with high durability by the same operation as usual or asimpler operation than usual.

[0044] Now, specific embodiments of the present invention will bedescribed with reference to working Examples (Examples 1, 4 and 6) andComparative Examples (Examples 2, 3 and 5). However, the presentinvention is by no means restricted by such specific Examples.

EXAMPLE 1

[0045] A solution composed mainly of ethanol and having a catalysthaving 40 wt % of platinum supported on a carbon black powder and an ionexchange resin made of a CF₂=CF₂/CF₂=CF−OCF₂CF(CF₃)−OCF₂CF₂SO₃Hcopolymer having an ion exchange capacity of 1.1 meq./g dry resindispersed therein; and a solution having 10 wt % of a polymer of thefollowing formula 10 having a molecular weight of about 100,000(tradename: CTL-110S, manufactured by Asahi Glass Company Ltd.) as asolvent-soluble fluorine-containing polymer dissolved in a mixed solventof perfluoro(2-butyltetrahydrofuran) and perfluoro(tributylamine) at aweight ratio of 1:1, were mixed to prepare a catalyst dispersion A. Theweight ratio of the catalyst (inclusive of the carrier), the ionexchange resin and the solvent-soluble fluorine-containing polymer inthe catalyst dispersion A, was 80:19:1. Further, a catalyst dispersion Bwas prepared in the same manner as the catalyst dispersion A, exceptthat the solvent-soluble fluorine-containing polymer was not contained(the weight ratio of the catalyst and the ion exchange resin in thesolution was 80:20).

[0046] Using, as an ion exchange membrane which is a solid polymerelectrolyte, a perfluorosulfonic acid type ion exchange membrane(tradename: Flemione® S membrane, manufactured by Asahi Glass CompanyLtd., ion exchange capacity: 1.0 meq./g dry resin, thickness: 80 μm),the catalyst dispersion A and the catalyst dispersion B were sprayed tothe air electrode side and the hydrogen electrode side, respectively, ofthe ion exchange membrane, so that the content of platinum was 0.5mg/cm² on each side, followed by drying for one hour at a temperature of120° C. to obtain an electrode/membrane assembly (electrode area: 10cm²).

EXAMPLE 2

[0047] An electrode/membrane assembly was prepared in the same manner asin Example 1, except that PTFE fine powder (secondary particle size: 2μm, primary particle size: 0.1 μm) was used instead of thesolvent-soluble fluorine-containing polymer, as a water repellent in thecatalyst dispersion A to be sprayed to the air electrode side.

EXAMPLE 3

[0048] An electrode/membrane assembly was prepared in the same manner asin Example 1, except that the catalyst dispersion B was sprayed to boththe air electrode side and the hydrogen electrode side to obtain theelectrode.

EXAMPLE 4

[0049] A catalyst having 40 wt % of platinum supported on a carbon blackpowder and granulated PTFE were kneaded at a weight ratio of 80:20, andthe mixture was coated on a porous film so that the platinum contentbecame 0.5 mg/cm². Then, the electrode was impregnated in a solutionhaving the same ion exchange resin as in Example 1 dispersed in ethanol,so that the ion exchange resin was present on the surface of theelectrode in an amount of 1 mg/cm². Then, the electrode was impregnatedin a solution having 0.05 wt % of a polymer of CF₂=CFO(CF₂)₂CF=CF₂(molecular weight: about 100,000) dissolved in a mixed solvent ofperfluoro(2-butyltetrahydrofuran) and perfluoro(tributylamine) at aweight ratio of 1:1, so that the polymer was present on the surface ofthe electrode in an amount of 0.01 mg/cm², followed by drying for onehour at a temperature of 120° C. to prepare a diffusion electrode A.Further, a diffusion electrode B was prepared in the same manner as thediffusion electrode A, except that the electrode was not impregnated inthe solution of the fluorine-containing polymer.

[0050] To the same ion exchange membrane as used in Example 1, thediffusion electrode A and the diffusion electrode B were hot-pressed tothe air electrode side and the hydrogen electrode side, respectively, ata temperature of 150° C. under pressure of 10 kg/cm², to obtain anelectrode/membrane assembly (electrode area: 10 cm²).

EXAMPLE 5

[0051] An electrode/membrane assembly was prepared in the same manner asin Example 4, except that the diffusion electrode B was used for boththe hydrogen electrode side and the air electrode side.

EXAMPLE 6

[0052] The catalyst dispersion A was sprayed to an ion exchange membranefollowed by drying to obtain an air electrode in the same manner as inExample 1, except that a perfluorosulfonic acid type ion exchangemembrane (tradename: Flemion® R membrane, manufactured by Asahi GlassCompany Ltd., ion exchange capacity: 1.0 meq./g dry resin) having athickness of 50 μm was used as the ion exchange membrane.

[0053] Then, to a gas diffusion layer made of polytetrafluoroethyleneand carbon at a weight ratio of 30:70, a solution composed mainly ofethanol and having a catalyst having 40 wt % of platinum supported oncarbon black and an ion exchange resin made of aCF₂=CF₂/CF₂=CF−OCF₂CF(CF₃)−OCF₂CF₂SO₃H copolymer having an ion exchangecapacity of 1.1 meq./g dry resin dispersed therein, was coated toprepare a hydrogen electrode. The weight ratio of the catalyst and theion exchange resin in the hydrogen electrode was 70:30. The hydrogenelectrode was bonded to the ion exchange membrane having the airelectrode formed thereon to prepare an electrode/membrane assembly.

[0054] The electrode/membrane assembly prepared in each of Examples 1 to6 was assembled into a cell for measurement, and while supplyinghydrogen gas to the hydrogen electrode and air to the air electrode,continuous operation of the cell was carried out at a constant drivingvoltage of 0.65 V at a cell temperature of 70° C. at 3 ata, whereby thechange with time of the output current density was measured. The resultsare shown in Table 1. TABLE 1 Output current density (A/cm²) 10 Hours100 Hours 1,000 Hours later later later Example 1 0.80 0.80 0.79 Example2 0.80 0.65 0.53 Example 3 0.81 0.50 0.28 Example 4 0.72 0.71 0.71Example 5 0.72 0.50 0.40 Example 6 0.82 0.82 0.81

[0055] As described in the foregoing, according to the method of thepresent invention, it is possible to impart water repellency to a gasdiffusion electrode easily and uniformly with high durability. Further,by using the electrode of the present invention, a polymer electrolytefuel cell is obtainable which shows little deterioration with time ofthe output characteristics.

What is claimed is:
 1. An electrode for a polymer electrolyte fuel cell,which is a porous gas diffusion electrode comprising a catalyst powderand an ion exchange resin, wherein a solvent-soluble fluorine-containingpolymer having substantially no ion exchange groups exists at least at apart of the inner surface of pores of the electrode.
 2. The electrodefor a polymer electrolyte fuel cell according to claim 1, wherein theamount of the ion exchange groups contained in the fluorine-containingpolymer is at most 0.1 meq./g dry resin.
 3. The electrode for a polymerelectrolyte fuel cell according to claim 1, wherein thefluorine-containing polymer is a perfluorocarbon polymer having analicyclic structure.
 4. The electrode for a polymer electrolyte fuelcell according to claim 1, wherein the fluorine-containing polymercontains polymer units of the following formula 1, 2 or
 3.

wherein 1 is an integer of from 0 to 5, m is an integer of from 0 to 4,n is an integer of from 0 to 1, l+m+n is from 1 to 6, and R is F or CF₃;

wherein each of o, p and q which are independent of one another, is aninteger of from 0 to 5, and o+p+q is from 1 to 6;

wherein each of R₁ and R₂ which are independent of each other, is F orCF₃.
 5. The electrode for a polymer electrolyte fuel cell according toclaim 1, wherein the fluorine-containing polymer contains polymer unitsof any one of the following formulae 4 to
 12.


6. The electrode for a polymer electrolyte fuel cell according to claim1, wherein the fluorine-containing polymer is a polymer obtained bypartial fluorination of a non-acrylic resin.
 7. The electrode for apolymer electrolyte fuel cell according to claim 1, wherein thefluorine-containing polymer is a copolymer having polymer units based ona fluoroolefin and polymer units based on at least one monomer selectedfrom the group consisting of a vinyl ether, a vinyl ester, an allylether, an allyl ester, an isopropenyl ether, an isopropenyl ester, anacrylic ester and a methacrylic ester.
 8. The electrode for a polymerelectrolyte fuel cell according to claim 1, wherein thefluorine-containing polymer has a molecular weight of from 2,000 to200,000.
 9. The electrode for a polymer electrolyte fuel cell accordingto claim 1, which contains from 0.01 to 30 wt % of thefluorine-containing polymer.
 10. A polymer electrolyte fuel cellcomprising a solid polymer electrolyte membrane made of an ion exchangemembrane and a pair of electrodes disposed on both sides of themembrane, wherein at least one of the pair of electrodes is a porous gasdiffusion electrode comprising a catalyst powder and an ion exchangeresin, and a solvent-soluble fluorine-containing polymer havingsubstantially no ion exchange groups exists at least at a part of theinner surface of pores of the electrode.
 11. The polymer electrolytefuel cell according to claim 10, wherein from 0.01 to 30 wt % of thefluorine-containing polymer is contained in the porous gas diffusionelectrode.
 12. The polymer electrolyte fuel cell according to claim 10,wherein the fluorine-containing polymer is a perfluorocarbon polymerhaving an alicyclic structure.
 13. The polymer electrolyte fuel cellaccording to claim 10, wherein the fluorine-containing polymer is apolymer obtained by partial fluorination of a non-acrylic resin.
 14. Thepolymer electrolyte fuel cell according to claim 10, wherein the ionexchange resin and the ion exchange membrane are made of a fluorocarbonsulfonic acid type ion exchange resin or a fluorocarbon phosphonic acidtype ion exchange resin.
 15. The polymer electrolyte fuel cell accordingto claim 10, wherein the ion exchange resin and the ion exchangemembrane are made of a perfluorocarbon sulfonic acid type ion exchangeresin comprising a copolymer having polymer units based on CF₂=CF₂ andpolymer units based on CF₂=CF−(OCF₂CFX)_(m)−O_(p)−(CF₂)_(n)−SO₃H,wherein m is an integer of from 0 to 3, n is an integer of from 1 to 12,p is 0 or 1, and X is F or CF₃.
 16. The polymer electrolyte fuel cellaccording to claim 10, wherein the electrode contains, as a binder, apolytetrafluoroethylene, a tetrafluoroethylene/hexafluoropropylenecopolymer or a tetrafluoroethylene/perfluoroalkyl vinyl ether copolymer.17. A method for producing a polymer electrolyte fuel cell, whichcomprises forming a mixture comprising a solution having asolvent-soluble fluorine-containing polymer dissolved in a solvent, acatalyst powder and an ion exchange resin to form a porous gas diffusionelectrode, and bonding the electrode to an ion exchange membrane.
 18. Amethod for producing a polymer electrolyte fuel cell, which comprisesspraying a solution having a solvent-soluble fluorine-containing polymerdissolved in a solvent to a porous diffusion electrode comprising acatalyst powder and an ion exchange resin, and bonding the electrode toan ion exchange membrane.
 19. A method for producing a polymerelectrolyte fuel cell, which comprises impregnating a porous diffusionelectrode comprising a catalyst powder and an ion exchange resin, in asolution having a solvent-soluble fluorine-containing polymer dissolvedin a solvent, and bonding the electrode to an ion exchange membrane.